6 replies to this topic

[suresh2]

Hi all,

I got a doubt when i was going through erosional velocity in API 14E.

1. can we use the same formula ( API 14E, section 2, Eq. 2.14 ) to calculate the erosional velocity for
single phase liquid and gas lines??

2. I did not understand their explanation about, Minimum cross-sectional area required to avoid Erosion.
I mean why the unit of area is in^2/1000 bpd??

3. Please explain me the API 14E, Section 2, 2.5 a (4) which says that,

The minimum required cross-sectional area for two-phase piping may be determined by multiplying A
by the liquid flow rate.

Note: basically i could not understand the min-req. area formula given for single phase or two-phase?

please let me know, if you have problem in understanding my question.

Regards
Suresh

Edited by suresh2, 28 December 2009 - 03:15 PM.

[GKKannan]

Hi Suresh,

Basically erosion velocity is applied and compared for two phase flow lines. For single phase lines, it is far away from the velocity we choose. For liquids, 1-2 m/sec and gases, 20 - 30 m/sec.

For 2 phase, you have to use Taitler and duckler charts available is Perry for comparing the velocity profile and the regime. You should try to avoid Slug flow regime while designing these lines, though it may not be possible to avoid this regime in some cases by changing the pipe dia. In that case, you should take precaustions like special piping supports for 2 phase lines.

I didnt have an idea about the API-14E. I shall try to get that standard and understand your problem.

GK Kannan.

[suresh2]

I got the answer for in the first para, which included the velocity ranges, of your reply.

I hope i would get answer for my second question soon after you refer to API 14E.

Thanks a lot.
Suresh

Edited by suresh2, 12 January 2010 - 10:27 PM.

[Art Montemayor]

Suresh:

I believe you are getting confused in trying to apply API Recommended Practice 14E simply because it doesn't seem to apply to your case(s).

For example, why try to apply a 2-phase recommendation to a single-phase system? I think you already have come to that realization. Additionally, your question regarding the units of the calculated minimum cross sectional area required flies into the face of reality: API 14E is designed and applicable to petroleum oil and gas production lines and - as such - has to contend with 2-phase and 3-phase flow (including solids) as well as with the customary petroleum flow units which are barrels of oil per day. That, basically, is the prime reason why the units of required minimum area are expressed as in² per 1,000 barrels of liquid per day.

I also believe you are not paying close attention to the specific application at hand: 2-phase flow. Industry experience, as is noted, indicates that for solid-free fluids (2-phase) the value of C = 100 for continuous service and can be 125 for intermittent service. These values are considered "conservative". Additionally, for solids-free, 2-phase fluids where corrosion is not anticipated or where corrosion is controlled by inhibitiion or by employing corrosion-resistant alloys, values of C = 150 to 200 may be used for continuous service.

However, you haven't explained by you are considering 2-phase relationships for single-phase fluids. Could you be more specific?

[suresh2]

Dear Art, first of all let me convey my heartful wishes to you.

I assumed the Fluid = NG+Oil ( solids free, c = 100 )
Density = density of the mixture

Calculated the erosional velocity, Ve.

Now,

API 14 E says that,
The minimum required cross sectional area, A, for two-phase piping may be determined by multiplying A by the liquid flow rate expressed in thousand of barrels per day.

My Points are:
1. Minimum cross sectional area is a function of Erosional velocity.
2. Erosional velocity is calculated using the data of Mixture ( e.g. density of the mixture )

Q) I did not understand how the Area is specifically refered to liquid, why not the total mixture.

I hope you would understand my question.

Thanks a lot.
Suresh

I think you may not received my request towards the Excel workbook. Please email me at

sureshreddy_50@yahoo.co.in

Edited by suresh2, 12 January 2010 - 10:26 PM.

[joerd]

If you look at Eq. 2.16, you see that there the conversion is made (with a number of unlisted assumptions) to convert from the mixture flow rate to barrels of liquid per day (since that is a convenient unit of measurement in the industry, as Art pointed out). That is why you can multiply by the production rate to get the minimum area.
If you don't like that, once you have established the maximum velocity, you could simply calculate the required area (sq.ft) by dividing the volumetric flow rate (in cubic feet/second) of the mixture by the maximum velocity (in ft/s).

[suresh2]

Dear jeord,

I guess i did not see the conversion of total mixture flowrate in terms of BPD.

Thanks for your information.